An energy-saving and environment-friendly spray drying process

Abstract

The invention relates to an energy-saving environment-friendly mist spray drying technology which is realized through a corresponding mist spray drying system. The mist spray drying system mainly comprises a drying tower, a first-stage compressor, a second-stage compressor, an expansion machine, a heat exchanger and a gas-liquid separator. Tail gases exhausted from the drying tower are pressurized and heated stage by stage, the treated tail gases in the heat exchanger form a larger temperature difference and a larger pressure difference with a cold source gas, the heat exchanging effect is strengthened and particularly the release and the recycle of the condensation heat of a gaseous solvent in the mixed gases of high potential energy after pressurization can be promoted. After the condensation heat of the solvent is recycled, the mixed gases are transformed into a gas-liquid mixture to be subjected to gas-liquid separation; during the recycle of the condensation heat of the solvent, and the gas-liquid separation, which are performed in order, the pressure of the mixed gases is almost unchanged, the potential energy is not lost, the gases obtained through the gas-liquid separation still have higher potential energy, and the potential energy and the heat energy of the gases are transformed into kinetic energy through the expansion machine to be provided for the second-stage compressor, so that the recycle of the potential energy and the heat energy of the tail gases is realized, and the energy consumption of the system is reduced.

Description

technical field [0001] The invention relates to an airflow drying process, which is a closed drying process, suitable for flash drying and spray drying, especially suitable for drying of heat-sensitive materials, drying of flammable and explosive solvents and low-temperature drying. Background technique [0002] Spray drying is widely used in food (milk powder, whey powder, egg powder, fruit juice powder, instant coffee, tea powder, hydrolyzed protein, etc.), chemical industry, medicine, ceramics, special Alloy powder, lithium battery, environmental protection and other industrial production fields. However, since spray drying requires a large amount of high-temperature hot gas to carry energy for heating, the exhaust gas mixed with energy-containing carrier gas and evaporated water vapor after drying has little use value due to the low temperature. Generally, it is directly discharged into the atmosphere after the solvent is recovered. , causing a lot of waste of heat ener...

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Problems solved by technology

[0009] In categories (1) and (2) of the above-mentioned prior art, due to the characteristics of large flow rate, low temperature, and low thermal energy grade of the exhaust gas, generally only 20% to 30% of the heat energy carried by the exhaust gas can be recovered. %

The process described in category (3) requires multiple equipment to be used in series, at least 3 to 10 levels are set. The series connection of two drying systems is already very complicated. Multiple sets of series connection must provide the operation of each unit of the system, system linkage balance control and Equipment investment, equipment occupation, etc. bring great difficulty and operation and management costs, which are not suitable for popularization and use, and the final steam of this process still needs to be discharged from the last stage of drying tower, and the reduced fresh air supplements heat energy in the whole system The proportion is not large, and the rational use of steam condensation heat in the exhausted tail gas is the key point in this field

The method and device of category (4) realizes the full recovery of solvent condensation heat, and the condensed water is discharged from the system at a temperature close to normal temperature. Complicated, and the recovery temperature difference is only 30-50°C, low recovery efficiency can only be achieved by increasing the circulation volume of the exhaust system and heat pump system to achieve water vapor condensation recovery, which will instead increase the power consumption of the drying system and heat pump system

In category (5), the solvent vapor carried out in the tail gas needs to be condensed and recovered with a cooling or freezing medium, which wastes heat energy and increases the cooling or freezing source, resulting in high operating costs; The tail gas heat exchange process, because the two operate under the same pressure, the temperature difference is small, the recovery of heat energy is of little significance, and the solvent in the tail gas has to consume a large amount of cooling or freezing medium for condensation recovery

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